1. Field Of The Invention
This invention relates to adapters used in inner string cementing and methods of use thereof, and more particularly, to an adapter which has a seal thereon which may be engaged with any floating equipment having a substantially flat upper surface.
2. Brief Description Of The Prior Art
A frequently used method of cementing casing strings is inner string cementing which is performed by pumping cement through a work string, such as a drill pipe which has been run inside the casing, rather than pumping cement through the casing itself. Inner string cementing is particularly useful for large casings and casing at extreme depths because it minimizes the amount of cement that has to be drilled out of large diameter casing or deep casing compared to cementing in the conventional manner.
Inner string cementing is illustrated in Halliburton Services Sales & Service Catalog No. 43, pages 2411-2412, published in 1985. A sealing adapter is attached to the end of the work string, such as the drill string or other small diameter pipe, and the adapter has a seal thereon which engages the corresponding floating, guiding or baffle equipment (collectively referred to herein as "floating equipment") on the casing string. When sealingly engaged, cement is pumped through the small diameter pipe, rather than through the casing itself, and discharged through a float collar, float shoe or other device.
One such inner string cementing tool consists of a stab-in type sealing adapter which is designed to enter into, seat and seal inside any Halliburton floating equipment using a molded plastic seat insert. The adapter is attached to the inner string immediately below a special centralizer which keeps the adapter centrally located in the casing. Another tool consists of a special baffle collar, float collar or float shoe which has a sealing sleeve molded into the concrete. The concrete molding has a chamfered surface to help guide or pilot the sealing adapter into the sealing sleeve. Still another type of cementing tool incorporates a special baffle collar which has a built-in latch-down baffle molded into the concrete. The concrete portion has a chamfer to aid in insertion of the sealing adapter. A latch-down plug may be pumped down the inner string and latched into the baffle collar.
In all of these devices, sealing engagement must be obtained at the end of the work string so that cement is displaced through the floating equipment and into the annular space between the casing and well bore rather than leaking into the annular space between the work string and the casing.
There are many advantages to inner string cementing. As previously mentioned, the amount of cement used is minimized. Further, large cementing plugs or plug containers are not necessary, and when no cementing plugs are used, drilling out of the cement is simplified. When cement is pumped down the inner string, there is less likelihood of contamination from the drilling mud, and inner string cementing also provides more rapid placement of the cement.
The inner string cementing tools previously described have worked well, but they do require the insertion of an adapter into a smooth bore in the floating equipment. Such insertion requires a separately sized adapter for each size of bore in the floating equipment. There is a need for a cementing adapter which is not required to be specially sized for particular bores, and there is also a need for an adapter which may be used on floating equipment which does not have a smooth bore therein. The present invention meets these needs by providing an adapter which is universal for virtually any floating equipment which has a substantially flat upper surface and which an orifice or opening which is smaller than the outside diameter of the adapter seal.